Many modern electronic doorbells are powered by batteries. It's because of this that they do not require any physical connection to a house's power grid. However, the batteries for a doorbell will eventually run out. It's important to take care of the problem by replacing the batteries before someone who you're expecting is at your door.
Unscrew the doorbell using the screwdriver or drill if the doorbell is mounted.
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Open the battery compartment of your doorbell.
Remove the old batteries from the doorbell and replace them with the new batteries.
Close the battery mount. Test the doorbell to make sure it works.
Reattach the doorbell to where you removed it using the drill or screwdriver.